In the future, wireless communication systems may use smaller cells and denser deployments. This will lead to an increased probability of Line-of-sight (LOS) communication between base stations and user terminals as well as increased interference level. The wireless communication systems today are usually interference limited, and in the future the interference over noise level will probably be even higher.
The antennas that are used in user terminals are typically designed to have high efficiency for a large number of frequency bands, so-called multi-band antennas. When designing multi-band antennas for user terminals, it is difficult to achieve a desired polarization for the antenna pattern while at the same time keeping the efficiency high. This means that if there are two multi-band antennas in a user terminal, the polarization orthogonality between the antennas is typically not good. When user terminals are in LOS to a base station, it is difficult to achieve more than one stream per polarization due to low scattering. In such situations, it is desirable to have user terminal antennas with mutually orthogonal polarization.
In this context, the term efficiency at an antenna port of an antenna is defined as 1−(S11)2, where S11 is the return loss at the antenna port in question.
It is therefore a desire to provide a user terminal device for use in a wireless communication system, where the user terminal device is arranged to provide a desired functionality for different scenarios such as LOS and non-LOS scenarios where the scattering may be low or high.